1. Field of the Invention
The invention relates to radar transmitters generally and more particularly to unattended or minimally attended radar transmitters employing a plurality of solid-state, radio frequency, power modules paralleled in failure resistant networks.
2. DESCRIPTION OF THE PRIOR ART
In the prior art the need for reliable unattended or minimally attended radar systems generates the requirement for fault tolerant transmitters. In typical current state-of-the-art radar transmitters, a single high-power RF generating device such as a magnetron, amplitron, or the like is controlled to generate the required train of radio frequency pulses. Quite obviously, failure of this single RF generating element causes failure of the entire system.
It has been recognized that, if the RF pulse transmitter comprised a number of solid-state RF amplifiers (for example) in a paralleled arrangement, these could be interconnected or paralleled in a network permitting the remaining units to continue to provide power output. Such a device was described by Ulrick Gysel in a Stanford Research Institute paper entitled "A New N-Way Power Divider/Combiner Suitable for High Power Applications". That paper was published in the IEEE-MTT-5International Symposium Digest, Page 116 (1975). The described device has since been referred to as Gysel combiner and is an improvement over the so-called Wilkinson combiner. The Wilkinson combiner was itself described in a paper entitled "An N-Way Hybrid Power Divider" published in the IRE Transactions on Microwave Theory and Technique, Volume MTT-8, pages 116-118 (January 1960). Further background information for those skilled in this art is contained in a paper by J. J. Taub and B. Fitzgerald entitled "A Note on N-Way Hybrid Power Dividers" published in the IEE Transactions on Microwave Theory and Techniques, Volume MTT-12, pages 260-261 (March 1964).
Since Microwave solid-state amplifier devices are currently limited to relatively low power per unit as compared to a magnetron, amplitron, etc., the paralleling of such devices in a network such as Gysel combiner was a natural outgrowth. The inherent reliability and long life of solid-state devices is particularly advantageous in the unattended or minimally attended radar application.
Various techniques have been proposed for employing paralleled RF solid-state devices. Most of these are based on some component switching mechanism for replacing failed power transistors to maintain the nominal transmitted power level. Such arrangements including spares which normally do not operate but are brought into action by these switching mechanisms to replace failed units.
Those of skill in this art are well informed on the prior art respecting pulse-compression radar and the reasons therefor. The text "Radar Handbook" by Merrill I. Sknoik (McGraw Hill Book Company 1970) devotes its Chapter 20 to the subject of "Pulse Compression Radar" and the reader desiring further background information in that respect can obtain it therefrom, and from the footnote references therein provided.
The manner in which the present invention provides an improved fault-tolerant or failed-resistant radar transmitter combination will be evident as this description proceeds.